This invention relates to magnetic reproducing apparatus for reproduction of video signals from a magnetic tape which is recorded with the video signals by means of a helical scan type video tape recorder and, more particularly, to a magnetic tape recorder capable of performing special image reproduction such as high-speed search, slow-motion and still reproduction.
When, in a conventional helical scan type magnetic recording and reproducing apparatus, recorded video signals are reproduced in variable speed reproduction modes such as high-speed search, continuous slow-motion, intermittent slow-motion, still reproduction and frame feed reproduction, the travel speed of the magnetic tape is changed while the rotary head drum continues to rotate. As an example, a magnetic recording and reproducing apparatus disclosed in Japanese patent unexamined publication No. 59-45785 may be noted which is adapted to perform, for example, intermittent slow-motion reproduction.
Because, in the variable speed reproduction mode, relative speed between the magnetic head and the magretic tape used during reproduction is however different from relative speed used during recording, the rotary head scans, for reproduction, the magnetic tape at a helix angle different from that of a recording track pattern formed on the magnetic tape during recording. This leads to a tracking error which causes the envelope of a reproduced video signal to form into a rhomb and hence a noise band occurs on a reproduced picture display screen at a decreased level portion of the reproduced video signal, thus degrading quality of picture.
Therefore, in a prior art magnetic recording apparatus, the travel speed of the magnetic tape and the timing for intermittent travel have been controlled such that an interval of time during which the noise band occurs is confined within the vertical blanking period or duration.
The prior art magnetic reproducing apparatus fails however to provide complete prevention of the occurrence of the noise band. Especially in the high-speed search mode, the noise band occurs on the reproduced picture display screen at a plurality of locations, resulting in impairment of clear visualization of the picture.